The formulation of effective laundry detergent compositions which are sufficiently robust to remove a wide variety of soils and stains from fabrics under a variety of usage conditions remains a considerable challenge to the industry. This is especially true since the advent of legislation which limits the use of effective phosphate builders in many regions of the world.
Most conventional detergent compositions contain mixtures of various detersive surfactants in order to remove a wide variety of soils and stains from surfaces. For example, various anionic surfactants, especially the alkyl benzene sulfonates, are useful for removing particulate soils, and various nonionic surfactants, such as the alkyl ethoxylates and alkylphenol ethoxylates are useful for removing greasy soils. Accordingly, mixtures of anionic and nonionic surfactants are used in many modem detergent compositions.
While a review of the literature would seem to suggest that a wide selection of surfactants is available to the detergent manufacturer, the reality is that many such materials are specialty chemicals which are not suitable for routine use in low unit cost items such as home laundering compositions. The fact remains that most home-use detergents still comprise one or more of the conventional ethoxylated nonionic and alkyl sulfate or alkyl benzene sulfonate anionic surfactants, presumably due to the economic and performance considerations.
It has recently been discovered that the class of nonionic surfactants which comprise the polyhydroxy fatty acid amides can deliver desirable cleaning properties when properly formulated in laundry and dishwashing compositions. The polyhydroxy fatty acid amides, especially those based on N-methylglucamine, are available from renewable resources such as vegetable oils and sugars, and are biodegradable. In use, this class of nonionic surfactants provides quite low interfacial tensions, which results in excellent cleaning of greasy/oily stains and soils.
Unfortunately, one of the most commonly used anionic surfactants, the alkyl benzene sulfonates (LAS) may not always be optimal for use in combination with the important class of polyhydroxy fatty acid amide nonionic surfactants. Under well-built conditions, at high temperatures, such combinations perform well. However, in cases where there are significant amounts of free water hardness, performance is substantially reduced. It may be speculated that some form of complex or undesirable phase behavior in the mixed system diminishes the overall effectiveness of the compositions. Moreover, use of the alkyl benzene sulfonates in combination with polyhydroxy fatty acid amides is not preferred when detersive enzymes are present in the compositions. Accordingly, it has been necessary to seek suitable anionic surfactants to substitute for the alkyl benzene sulfonates.
By the practice of the present invention, oleoyl sarcosinate is employed as the anionic surfactant in conjunction with polyhydroxy fatty acid amide surfactants to provide improved cleaning benefits, particularly when laundering fabrics. The compositions are advantageously water-soluble over a broad range of temperatures, are easy to formulate, and would appear to have no untoward interaction with most detergency ingredients. Use of the combination of oleoyl sarcosinate with the polyhydroxy fatty acid amide and enzymes appears to provide superior stability and oily stain removal performance. Moreover, the compositions provide low interfacial tensions and excellent cleaning even in nonphosphate built compositions, especially with zeolite or silicate detergency builders. Improved cleaning of body soils from fabrics is thus secured. Improved removal of stains such as shoe polish, lipstick, clay, coffee and meat sauce is also noted. The compositions also provide excellent color care for dyed fabrics and excellent skin mildness for hand-wash operations. Accordingly, the present invention overcomes many of the problems associated with known technologies and provides excellent detergent compositions for use in a wide variety of cleaning operations, as will be seen from the following disclosures.